Static Sorption of Phenol and 4-Nitrophenol onto Composite Geomaterials based on Montmorillonite, Activated Carbon and Cement

International audienceThis paper studies the sorption of phenol and 4-nitrophenol (4NP) onto solid sorbents derived from mixtures of montmorillonite, activated carbon (AC) and cement, denoted herein MACC. These materials are mesoporous and some of their physicochemical properties have been measured and discussed. The weight fraction X1 (%) of montmorillonite in the mixtures strongly influences the sorbate removal rate. The sorption isotherms were experimentally established by batch testing on geomaterials with various X1 values at 20 °C and at different pH values (from 3 to 8). The Langmuir model correctly fits the sorption isotherm data (R2 > 0.95). The results show increased sorption behavior for both phenol and 4NP on the composite geomaterials compared to the pure components, yielding the order: MACC > AC > montmorillonite

Propriétés adsorbantes d'argiles pontées organophiles (synthèse et caractérisation)

Une série de complexes inorgano-montmorillonites (CIM) à grandes surfaces spécifiques et stables thermiquement est préparée par intercalation d'une montmorillonite algérienne par trois solutions pontantes à base d'aluminium, de fer ou de titane. La co-adsorption de ces trois argiles pontées par du bromure (ou chlorure) de cétyl-triméthyl ammonium conduit à la formation de complexes organo-inorgano-montmorillonites (COIM) hydrophobes et organophiles. Les conditions de préparation de ces matrices sont liées au rapport molaire OH(ou H+)/Me, à la concentration finale et au temps de vieillissement de la solution pontante et au rapport CTAB/CIM. Toutes les matrices CIM et COIM préparées sont caractérisées par plusieurs méthodes telles que : DRX, S.S.(BET), spectroscopie IRTF, ATD/ATG, CEC, acidité de surface et zétamétrie. Les isothermes d'adsorption de plusieurs composés organiques : pentachlorophénol PCP, diuron et ses trois sous-produits de dégradation (dichlorophénylméthyl urée, dichlorophényl urée, dichloroaniline), du méthyl parathion, du rose sulfacide (colorant anionique) et des acides humiques AH sur les matrices COIM ont montré de grandes affinités adsorbants-adsorbats, surtout en milieu acide et avec les argiles à piliers de titane et de fer. L'étude de l'adsorption en mélange de deux solutés (PCP/AH) a montré globalement que l'adsorption du PCP est influencée par la présence des AH dont l'hydrophobie et les poids moléculaires sont élevés.LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

Effect of humic acids on pentachlorophenol sorption to cetyltrimethylammonium-modified Fe- and Al-pillared-montmorillonites

International audienceBecause natural organic matter is commonly present in surface water and might interfere with the removal of organic contaminants, we investigated the effect of humic acids (HA) on the adsorption of pentachlorophenol (PCP). The sorbents are synthetic clay compounds: surfactant-modified pillared montmorillonite (SMPM). First the cation exchange sites of an Algerian bentonite were blocked by intercalation of metallic polycations from either Fe(III) or Al(III); then cetyltrimethylammonium cations were adsorbed in order to obtain two hydrophobic and organophilic clay compounds. According to batch adsorption isotherms in single systems, both PCP and HA sorptions increased when pH decreased, especially for Fe-SMPM in comparison with inorganic pillared clays without cationic surfactant. The Fe-SMPM was more effective than the Al-SMPM for PCP sorption: at pH 6, the maximum PCP sorption capacities were 530 mg g− 1vs. 300 mg g− 1, respectively. From data treatment with an extended Freundlich model, in binary systems at pH 6 and at various PCP/HA ratio (ranging between 1/4 and 4/1 g g− 1), the competition affected both forms of SMPM quite strongly. In addition, the competition between PCP and HA was more important for the Fe-SMPM than the Al-SMPM, with respective maximum PCP sorption capacities of 133 vs. 53 mg g− 1. Due to their high thermal stability and efficiency towards organic compounds, SMPM may have environmental applications in treating surface water and wastewater for the removal of organic pollutants such as chlorinated phenol

Simultaneous sorption of 4-nitrophenol and 2-nitrophenol on a hybrid geocomposite based on surfactant-modified pillared-clay and activated carbon

International audienceNew generations of hydrophobic composite geomaterials intended to sorb certain hazardous wastes are assembled by mixing surfactant-modified aluminum-pillared montmorillonite (Al-SMPM) with activated carbon (AC). The sorption of 4-nitrophenol (4NP) and 2-nitrophenol (2NP) on these sorbents was studied in both single and binary component systems from aqueoussolutions using batch tests. Results showed the efficiency of these composite sorbents relative to the two phenolic compounds, with a dominant contribution from Al-SMPM. In single-component systems, sorption isotherms of 4NP and 2NP as a function of pH were analyzed with the Freundlich equation, whose statistical interpretation was also developed. Sorption capacities sharplydecreased when the solution pH value was raised from 3 to 9. In binary-component systems, the fit between measured and predicted simultaneous sorption capacities of both 4NP and 2NP indicated that the Sheindorf-Rebhun-Sheintuch model, an extended Freundlich model, is fully applicable. The 2NP favorably influences the sorption of 4NP. The synergistic effect between these two nitrophenol compounds has been confirmed by the higher competition coefficients, which increase with increasing pH. A number of hypotheses, based on the Abraham's solvation parameters model, have been advanced to discuss this mechanism